Siding composed of vinyl or other plastic material is a common medium for use as an external covering of a structure. Such siding is fabricated as elongate panels having connectors formed along the lengths of the upper and lower edges. In use, the siding panels are placed in horizontal interlocking tiers.
In one common construction, the siding panels use Pittsburgh or hurricane locks to interlock the panels (FIG. 1). Since the two panels of FIG. 1 are identical, the same reference numerals are used for both panels. A conventional siding panel 10 includes an upper connector 11, a lower connector 12, and a medial body 13. Body 13 ordinarily has a pair of faces 15, 17 separated by a center butt 19. Upper connector 11 is bent to form a dogleg protrusion 23 which extends downwardly over the upper face 15 of the siding panel to form a groove 25. Lower connector 12 has a channel-like shape. The distal wall 27 of the lower connector is inclined back toward the lower face 17 of the body. Distal wall 27 is snugly fit within groove 25 to interlock adjacent siding panels.
A premium siding panel will frequently be formed by a pair of materials fused together. The outer layer or capstock is composed of a weather, wear and impact resistant material which also provides a good appearance. The underlayer or substrate is composed of a stiffer material to increase the strength of the panel. Even with this composite construction, though, siding panels have suffered from a lack of sufficient stiffness. As a result, plastic siding has been difficult to install and unsuitable for certain areas of the country (e.g. coastal areas with high winds).
In an effort to improve the rigidity of plastic siding, the connectors of some panels have been altered to receive a fiberglass rod. More specifically, the connectors are formed to have circular channel shapes and define a modified Pittsburgh lock. Fiberglass rods are placed in the openings defined by the circular connectors. However, a full length panel (e.g., 12' 1") has virtually no increase in stiffness because of slippage between the rods and the panels along shear planes. As a result, the modified construction has not provided the desired benefits.